1. Technical Field.
This invention relates to a diffusing baffle for applying sprout inhibiting chemicals to stored potatoes, and more particularly to a diffuser which utilizes elongated channel shaped baffles to direct sprout inhibiting chemicals to the inlet of ventilation pipe.
2. Background Art.
Potatoes are usually harvested from the ground by the use of digging machines which lift the potatoes from under the ground and convey them up and into the bed of a truck traveling alongside of the harvester. Every attempt is made, both mechanically and by hand sorting, to separate the potatoes from clods of earth and rock. Once a truck is fully loaded, it is taken to a nearby storage where the potatoes are removed from the truck and piled within a storage building.
The potato tuber, when harvested, is a living organism in a nongrowth, or as it is more commonly called, a dormant state. But even in a dormant state it respirates and gives off heat at the rate, depending upon variety of between 1000 BTU's to 1800 BTU's per ton, per day. The potatoes are piled into earthen floored storage buildings approximately 16' to 20' high, with a typical storage facility holding between 2,500 tons to 12,000 tons in a pile of potatoes which can be as large as 130' wide by 400' long and 20' high. Thus the heat given off by the dormant potatoes in storage is considerable, ranging from 2.5 million to 21.6 million BTU's per day. As a result the problem is not keeping the storage facility heated, but rather cooled on all but the coldest of winter days.
If the potatoes overheat, bacterial activity in the potato pile will rapidly increase causing rot or hot spots in the pile. If the potatoes are chilled below 40.degree. F. the living potatoes will attempt to compensate by converting stored starch to sugar. If the moisture content of the air in the storage exceeds saturation for any given temperature, condensate will drip from the ceiling down into the pile of potatoes further enhancing bacterial activity. If the air is too dry, the potatoes will dehydrate which results in shrinkage of the total tonnage in storage.
The ideal storage parameters for a modern storage facility are 42.degree. F. to 45.degree. F. and 95%, but not saturated, relative humidity. In order to achieve this environment elaborate ventilation systems are incorporated into the storage facility to mix warm inside air with cooler outside air to maintain temperatures within the desired range. Humidification equipment is also provided, but is not relevant to invention at hand.
To get cooling air up through the pile of potatoes, ventilation pipes, having vent holes approximately 11/4 inches to 15/8 inches in diameter are first laid on the earthen floor before the potatoes are piled into the storage facility. These ventilation pipes are connected to a air supply plenum and are designed to distribute a supply of air to the bottom of the potato pile. This air filters up through the loosely stacked potatoes and exits the top of the pile, thereby keeping the potatoes at the desired temperatures. The air discharged from the pile is then either exhausted to the outside, or returned by means of a return air plenum to the fan where it is usually mixed with cool outside air or, if the outside air is warmer than the inside air, it is directly cycled back into the supply plenum.
These types of storage facilites are well known in the art and are disclosed in Luck, U.S. Pat. No. 4,078,480 and Sheldon, III, Et Al., U.S. Pat. No. 4,226,179.
It should also be mentioned that refrigerated systems are oftentimes incorporated into the design to cool the inside air if and when the outside air is too warm to serve as an effective source of cooling air. Refrigeration is usually found in storages located in warm climates, or in those storages designed to hold potatoes until later in the season, usually late spring. In any event, the invention described herein works equally well in both ventilation only and refrigeration storages.
Since the potato tuber is alive, albeit in a dormant or nongrowth state, at the time it is placed in the storage, its biological clock is ticking, and sometime before or during the spring it will begin to sprout. Once sprouting commences, the commercial value of the stored crop is substantially decreased. It the potatoes are to be removed from the storage facilities to processing early in the storage season no action to prevent sprouting is necessary. However if storage is planned to extend beyond January then action must be taken to inhibit sprouting. This is done by the use of chemicals.
Sprout inhibiting chemicals such as Isopropyl M-Chlorocarbanilate (CIPC) are typically used to inhibit sprouting. CIPC is an effective sprout inhibitor and is usually applied to the stored potatoes sometime between October and the beginning of February. CIPC is a difficult chemical to apply since it is a solid at normal temperatures, and secondly must be applied to potatoes in a storage facility which itself is at a remote location, oftentimes at the end of an unpaved country road. Also, this application must be accomplished during the winter months in inclement weather when it is difficult to keep portable engine powered equipment working properly.
Two different apparatus and processes for applying CIPC are described in Luck, U.S. Pat. No. 4,078,480 and Sheldon, III, Et Al., U.S. Pat. No. 4,226,179. However there are some general similarities common to all applications of CIPC. First, CIPC must be converted from its solid form to an aerosol capable of being deposited on the skins of the stored potatoes. The most common method is the use of a thermal fogger which heats the CIPC and a solvent solution to produce an aerosol type atomization or fog of CIPC which is then introduced into the air handling system. Such a device is described in the background art of Sheldon, III, Et Al., U.S. Pat. No. 4,226,179 as well as the ultrasonic device of Sheldon. In practice thermal fogging apparatus are the predominant method of atomizing CIPC, and temperatures in the 250.degree. F. range can be maintained by use of propane as a fuel source.
The fog of CIPC is injected into the central air plenum of the storage facility, and is distributed throughout the storage facility by use of the air handling system of the storage facility. The fog of CIPC eventually makes its way down the ventilation pipes, out through the vent holes and filters up through the pile of potatoes, depositing CIPC on the potatoes in the process.
Normal air flow in a ventilated potato storage ranges from 10 to 30 SCFM per ton of potatoes in storage. If, for example, 12,000 tons of potatoes were in a particular storage, this results in an air flow in the central air plenum of up to 360,000 SCFM. That is a lot of air flow, and the result is an extremely fast and turbulent movement of air through the fans and the central air plenum.
Concentrations of CIPC as low as 3 ppm on the surface of a potato are sufficient to inhibit sprouting. The maximum concentration by Federal Regulations is 50 ppm. In practice, using high air flow technologies, sufficient quantities of atomized CIPC must be introduced into the central air plenum to result in average residual concentrations of 17 to 20 ppm on the potatoes if all of it reached the potatoes instead of agglomerating and being deposited on the air handling system surfaces.
The high air flow rates cause a significant problem in that the CIPC is an aerosol suspension with the air inside the storage and is subject to agglomeration and impingement with the surfaces of the air plenum, vent pipes, louvers and fan blades of the air handling system. As the particles of CIPC agglomerate they form droplets sufficiently large to fall out of suspension with the air or which impinge upon the surfaces of the air handling system, forming a coating of CIPC on the air handling equipment which resembles a powdery hoarfrost. This is a significant problem for a number of reasons. First, the CIPC hoarfrost can actually plug ventilation holes in the ventilation pipes; secondly, a significant amount of CIPC, up to 85%, is wasted, and finally, the residue must be cleaned off of the air handling system and that itself is a most unpleasant and time consuming task.
In order to reduce the amount of CIPC used, and the excess residual concentrations of CIPC on the potatoes, I developed an apparatus for reducing the air flow and turbulence within the central air plenum to below 5 SCFM during the introduction of atomized CIPC into the central air plenum, as described in my U.S. patent application Ser. No. 07/281,982, filed 12/09/88now U.S. Pat. No. 4,887,525. This apparatus solved two problems, first it eliminated the hoarfrost problem and the exhaust of CIPC to the open atmosphere. This reduced the amount of CIPC injected into the storage, and as a result, reduces the amount of excess CIPC deposited on the potatoes.
In both the high air flow and low air flow technologies the CIPC fog is injected into the storage air supply plenum immediately downstream of the fan discharge. In the case of the high air flow systems, there is an immediate total mixing of CIPC fog and the air. However, in the case of the low air flow technologies as described in my U.S. patent application Ser. No. 07/281,982, filed 12/09/88, the mixing of CIPC fog with air is not immediate, but rather gradual because of the reduced air flow and air turbulence. In practice it has been found that full mixing of CIPC fog with the air in the air supply plenum may not occur until the mixture is 30 to 40 feet downstream of the fan discharge. As a result the air from the air supply plenum being introduced into the ventilation pipes closest to the fan discharge, the upstream ventilation pipes, may not contain sufficient quantities of CIPC to effectively inhibit potato sprouting. Thus, in order to compensate for the lack of CIPC introduction into the upstream ventilation pipes, it is necessary to run the air system long enough to insure that a residual mixture of CIPC and air is completely recycled from the downstream ventilation pipes up through the downstream potatoes, back into the air supply system and from there into the upstream ventilation pipes. This necessarily results in the introduction of greater quantities of CIPC into the air system in order to assure sufficient quantities of an aerosol suspension of CIPC is introduced into the upstream ventilation pipes.
While this extended introduction of CIPC into the storage at reduced air flow rates does increase the concentration of CIPC deposited upon the potatoes piled above the upstream ventilation pipes, the results are not always satisfactory.
Accordingly, what is needed is a method of temporarily baffling the air flow system within the central air plenum, at an upstream location immediately adjacent to the discharge of the air supply fan, in order to insure immediate mixing and that adequate concentrations of CIPC are introduced into the upstream ventilation pipes.